There are numerous types of valves for controlling fluid flow along a fluid pathway, such as, check valves, plug valves, ball valves, stop or globe valves, angle valves, butterfly valves, and gate valves. Check valves, for example, may include a valve member, such as a valve disc, that may be moved between an opened and a closed position by fluid (e.g., liquid). For example, pressure from fluid flow through the valve, fluid pressure proximate at least one side of the valve disc, or a lack of fluid pressure on either side of the valve may act to open or close the valve. In some embodiments, check valves may be biased in a closed position via a spring, gravity, or other mechanism.
Fluid that flows against the disc during normal operation opens the valve, allowing fluid to flow through the valve in a forward direction. If the fluid reverses flow so that there is no longer any flow in the forward direction, the disc may at least partially close due to an imbalance of pressure (e.g., a pressure differential) on either side of the valve (e.g., an upstream side and a downstream side) and/or due to an external biasing force, where implemented. In a check valve, this type of closing of the valve, at least partially prevents fluid from flowing through the valve in an unintended direction.
Check valves are commonly used in piping systems to at least partially prevent backflow from damaging systems that are upstream of the valve. For example, check valves can be used in a piping system that includes another fluid flow component (e.g., a pump) that is positioned upstream of the check valve. Should flow reverse, reversing flow should not be permitted to come into communication with (e.g., travel through) the pump. For example, reverse flow into the turbine of a pump could cause serious damage to the pump.
Check valves may also be utilized in applications requiring relatively higher reliability in the components of the check valve (e.g., the valve seat or seats) and in applications involving one or more of high-pressure, high-temperature, caustic, corrosive, and/or abrasive environments. For example, in a nuclear power plant, a flow path is coupled to the nuclear reactor that will allow cooling water to enter a containment center in the event of an accident. Flow is permitted from the cooling reservoir into the containment center in order to cool the reactor. However, reverse flow is highly undesirable since it will potentially allow hot, radioactive material to flow outside the containment center. Check valves are often utilized in systems, such as this, in order to prevent the reverse flow of fluid through the check valve.
As pressure differences are often used to open and close check valves, as discussed above, in most working environments, it is desirable that the check valves operate and be reliable at both high and low differential pressures to provide a sealing force between valve seats within the valve. However, the internal components of the check valve are generally required to substantially withstand high differential pressures, high closing loads, and, in some instances, harsh environmental conditions that may damage or reduce the reliability of conventional valve components, such as elastomer or polymer valve seats.